Least Tern

Least Tern (Sternula antillarum) is a tiny American tern with white forehead, black crown, yellow bill and narrow pointed wings. Body shape, bill structure, plumage pattern and voice provide the strongest field characters. Age, sex and season may alter its appearance, so identification should combine several features and careful direct comparisons with similar species in the same habitat (Wikipedia, general species account).

It hovers and plunge-dives for small fish and nests on sparsely vegetated sand or gravel near water. Its movements and social behaviour vary through the year, with breeding birds generally more dispersed and non-breeding birds gathering where food is concentrated. Japanese records place it within the country's documented avifauna as a resident, migrant or visitor (Wikipedia, general species account; Wildlife of Japan occurrence records).